The dopamine transporter is a principal site for cocaine's rewarding and euphoric effects in the brain. Cocaine analog binding studies have revealed some details of the regional distribution of this transporter in untreated and in cocaine-treated brains. Studies completed during this FY have substantially enhanced information concerning the distribution of dopamine transporter protein, using immunohistochemical approaches. They also elucidated cell-group-specific alterations in transporter gene expression in animals withdrawn from a regimen of chronic cocaine administration.